Fort Cobb Reservoir 5-year fisheries management plan.

FORT COBB RESERVOIR
5-YEAR FISHERIES MANAGEMENT PLAN
SOUTHWEST REGION
OKLAHOMA DEPARTMENT OF
WILDLIFE CONSERVATION
2
Prepared by:
Larry Cofer, Regional Fisheries Supervisor
Ryan Ryswyk, Fisheries Biologist
And John Perry, Fisheries Technician
DECEMBER 31, 2009
Contact Information
Address:
Southwest Fisheries Region
Oklahoma Department of
Wildlife Conservation
19333 State Highway 49
Lawton, OK 73507
Phone:
580/529-2795
Email:
swrfishodwc@mptelco.com
3
Background
Fort Cobb Reservoir, a U.S. Bureau of Reclamation
project, was impounded in 1959 for flood control,
water supply, fish and wildlife propagation and
recreation. The dam is located at river mile 7.4 on
Cobb Creek, a tributary of the Washita River, in
Caddo County, Oklahoma (Lat 35E 09' 45", Long 98E
27' 00"). Cobb Creek and two other principal
tributaries (Lake Creek and Willow Creek) drain
approximately 314 square miles into the reservoir
(Figure 1). Outflows from the reservoir include
municipal and industrial pipelines to Chickasha and
Anadarko, and an outlet for Cobb Creek.
The water in Fort Cobb Reservoir is managed by the Fort Cobb Master Conservancy District,
with offices in Anadarko, Oklahoma. Land use within the Fort Cobb watershed is primarily
agricultural, with 52% cropland and 42% range and pasture land. The remaining land surface can
be broken down into various other rural categories, with less than 0.5% considered urban.1
4
Through long-term agreement, the U.S. Bureau of Reclamation leases its lands around Fort Cobb
Reservoir to the Oklahoma Department of Tourism and Recreation (State Park -south half) and
the Oklahoma Department of Wildlife Conservation (north half; Fig. 2). Fort Cobb State Park
provides camping, swimming, boating and other recreational activities. The Oklahoma
Department of Wildlife Conservation (ODWC) provides hunting, fishing and boating facilities
and camping in the Fort Cobb Wildlife Management Area. Boating is regulated by the Lake
Patrol Division of the Oklahoma Highway Patrol.
Figure 2. Map of Fort Cobb Reservoir and lands managed by State Parks and ODWC.
Legend
-Fish Attractor
5
Habitat
At normal pool elevation (1342.0' NGVD), Fort Cobb reservoir is about 7 miles long, has a
current storage capacity of 73,800 acre-feet, a surface area of 4,300 acres (6 square miles), a
mean depth of 19 ft, a maximum depth of around 60 ft., and a shoreline length of about 45
miles.2 Fort Cobb’s Shoreline Development Index (shoreline length / surface area) is 7.0,
indicating a reservoir with a moderate number of coves, points and arms.
Outflows through the dam commonly occur in the spring rainy season, but are infrequent
afterward, and the average water exchange rate (average annual outflow / lake storage volume) is
0.6, indicating a relatively long water storage period.
The Fort Cobb MCD maintains the lake level at 1342 ft. The level is reduced by just two feet, on
average, in summers due to water use and evaporation. The lowest elevation on record is 1335
from October, 1972. Lowest elevation in the last 15 years was 3 ft. below normal pool Fort
Cobb, and the lake remained nearly full through the mini-drought of 2001 – 2006. A record high
of 1352, or 10 ft. above normal, was recorded in June, 1995. In August, 2007, Fort Cobb rose to
1350 – 8 ft. above normal- after Tropical Storm Erin dropped over 12 inches of rain in the
watershed in a 48-hour period. The lake remained in flood stage for one month after the event.
Fort Cobb has no standing timber remaining
in the basin, and many of the sandy banks
are eroded. Shoreline willows and
cottonwoods are flooded occasionally,
providing temporary shallow cover for fish.
Fort Cobb supports little aquatic vegetation
since 1982, when high water and a Eurasian
milfoil control project combined to
eliminate its extensive cattails and milfoil
beds. Recently, transplantings of native
water willow and bulrush by the ODWC
have taken root in a handful of coves in the
upper end. Extensive natural beds of sago
pondweed were noted in the shallows at Fort
Cobb in summer, 2009.
Sand and sandstone are the primary substrates in most of the lake. The dam and some shorelines
in the State Park are lined with rock rip-rap, and sandstone points and drop-offs provide some
fishing habitat. Siltation is common from erosion in the watershed, and deltas formed in upper
coves are quickly populated by willow trees.
A sedimentation study conducted at Fort Cobb in 1993 determined that siltation had resulted in a
7% loss of water volume (at elev. 1342) since construction in 1959, or an average loss rate of
165 acre-feet per year.3 Assuming that trend has been consistent, about 10% of volume has been
lost to date, due to erosion of sandy topsoil from farms in the watershed. That equates to a loss of
over 480 water surface acres for recreation.
6
Water Chemistry
Water quality in Fort Cobb Reservoir has been thoroughly studied due to impacts from farming
activity in the watershed and resulting degradation of water supply and recreational values.
From sampling in 2006, Fort Cobb’s Trophic State Index (TSI) value was 65, indicating a
hypereutrophic reservoir.1 Another study in 2000-2002 found a TSI value of 67.5 The lake
ranks as “not supporting” for potential beneficial uses of fish and wildlife propagation (due to
turbidity), or for aesthetics (due to trophic status).
Secchi disk visibilities in 2002 averaged 19.5 inches in the upper end, 35.5 inches in the lower
end, and 28 inches overall. In 2006, secchi visibility averaged 24 inches. The NTU value was 13
and the true color was 20 units. Fort Cobb’s turbidity is primarily from phytoplankton in the
lower end, dominated by blue-green algae. Turbidity in the upper end is primarily from
suspended clay stirred up by wind and wave action across shallow sediments.
Sources of nutrient loading and
erosion into Fort Cobb Reservoir have
been studied, and most are non-point
contributors from farming.5 A 319
Demonstration Project has been
implemented in the Lake Creek
watershed to educate farmers and
implement best-use practices. Results
from that 10-year program will be
available in 2010.
Specific conductance at Fort Cobb
ranged from 450 to 1100 umhos, with
an average of 572. Salinity is 0.23 to
0.58ppt. Total alkalinity ranges from
113 to 129, with a lakewide average of
118 mg/l as CaCo3. Hardness
averaged 189 mg/l.
Dissolved oxygen values range from 8.8 to 12.0, with an average of 10.3. Fort Cobb is only
occasionally stratified in summer at a depth of 30 to 42 ft near the dam. Frequent high winds
generally keep the lake mixed. Reservoir pH values ranged from 7.3 to 10.7, with an average of
8.4. Average annual water temperature is 64 degrees.
A fish kill in April, 2001 resulted in the loss of nearly all adult white bass in Fort Cobb
Reservoir. An unidentified virus was suspected as the cause since species-specific white bass
kills were reported from several other reservoirs in the Oklahoma and around the Midwest near
the same period. Poor water quality was not the suspected primary cause, but may have
contributed to the severity of the kill.
7
Habitat Implications on Fishery and Management Objectives
Excessive nutrients result in dense algal blooms at Fort Cobb Reservoir, and gizzard shad are
prolific. The loss of white bass in the fish kill of 2001 further contributes to the high number of
shad in the lake. Bank erosion and sedimentation of soils from the watershed have resulted in
reduced bank contour and increased shallow water, but aquatic vegetation has not rebounded in
this favorable environment. The lack of shallow cover is a negative for species like bass and
sunfish, and instead favors open-water species like saugeye, catfish and hybrid striped bass.
Water level fluctuations below normal pool are relatively minor at Fort Cobb. Even in the mini-drought
of 2001-2006, the water level was stable. Occasional flooding contributes to better
conditions for fish spawning and growth. High water in the summer of 2007 contributed to a
strong year-class of bass and crappie.
Primary winds and wave action in summer are from the south, and strong north winds are
common after winter cold fronts. Anglers and boaters are able to find calm waters or fish windy
points on most days at Fort Cobb. Some anglers have learned to use the wind to improve their
success by fishing along windy banks for channel catfish, hybrid stripers and saugeye. Fort
Cobb’s fertility makes fishing better-than-average, compared to other waters in western
Oklahoma, but the ODWC is concerned about the potential of further fish kills and disease due
to poor water quality.
History of Fishery
Fishing at Fort Cobb Reservoir has been managed by the ODWC’s Southwest Fisheries Region
to optimize its potential since 1959. Predictably, fishing was excellent in the first 20 years (the
“new lake effect”), but that was followed by moderation in fishing success in the last 30 years.
Notably, the loss of vegetation after 1982 resulted in reduced fishing quality for largemouth bass,
sunfish and crappie. Poor habitat for bass has also led to a proliferation of rough fish like
common carp, river carpsucker and gar.
Fish were stocked heavily from Oklahoma State Fish
Hatcheries, particularly fingerling channel catfish and Florida-strain
largemouth bass (Table 1). Standardized surveys showed
no improvement in those populations from stockings. Hybrid
striped bass fry and fingerlings showed promise after they were
first stocked in 1980. Walleye were introduced in the 1970s and
a minor fishery developed. As walleye fishing success declined,
the ODWC began stocking saugeye in 1998 and the fishing
improved significantly. 6
Inland silversides were introduced as a new forage species to many Oklahoma reservoirs,
including Fort Cobb in the 1970s, but studies later determined that native predators seldom took
advantage of the small minnows. Saugeye were stocked beginning in 1998 to take advantage of
abundant silversides and shad, and a state record saugeye (10 lbs) was caught in 2006.
8
Florida largemouth bass were stocked from 1973 to 1988, but no bass over 10 pounds were
verified from anglers or sampled by the ODWC. Bass management efforts relied on a 14-inch
length limit since the 1980s, but bass fishing did not improve and poor spawning and recruitment
were found to be the limiting factors.
In recent years, bass tournaments have reported
occasional success, and an electrofishing sample in 2009
confirmed that the bass population had rebounded from
historic lows. Reservoir- (or Tennessee-) strain
smallmouth bass were transferred from Lake Lawtonka
in 2003, and a few are still present but not adding
significantly to fishery.
Brush piles have been constructed in key fishing spots
for many years to improve fishing for crappie and bass
(Fig. 2). Crappie fishing is fair, but the average size is
exceptional compared to other Oklahoma lakes.
Blue catfish were stocked in Fort Cobb by the ODWC in 1967, and an above-average fishery
exists for jug-liners and surf-rod anglers. High shad production in most years favors blue catfish.
Flathead catfish are low in abundance at Fort Cobb, but trotline anglers occasionally catch large
flatheads. The lake record caught in 2009 weighed 66 pounds.
Anglers once counted on white bass as a fishery staple, but
sand bass have not recovered from the lake-wide kill in
April, 2001. A few sand bass were captured in the most
recent gillnet sample. A similar low period was noted in
samples from 1987 and 1988, and sand bass recovered.
Hybrid striped bass were first stocked in 1980 and Fort
Cobb is one of the best lakes in Oklahoma for hybrid
fishing. Hybrids have been stocked frequently since the
2001 white bass kill, in part to fill the void. The lake record
hybrid was established in 2009 at 18.2 pounds, and anglers
regularly catch hybrids over 10 pounds.
The primary forage fish species in Fort Cobb are gizzard
shad, sunfish, inland silversides and minnows. Shad catch
rates have been high in recent samples, presumably due to
the low number of white bass since 2001.
Fort Cobb Reservoir was 50 years old in 2009. After years of standardized sampling efforts,
habitat improvements and regulation changes by the ODWC, largemouth bass abundance has
improved and anglers currently enjoy excellent fishing for saugeye, hybrid striped bass, and
catfish, and fair fishing for crappie. Boating access facilities are also excellent at Fort Cobb.
9
Current Status of the Major Fish Species
Bass
Electrofishing catch rates for largemouth bass were chronically below the state average (< 40 per
hour) since standardized sampling began at Fort Cobb in 1978. When bass habitat was
essentially eradicated with milfoil control in 1982 and high water in 1983, bass catch rates
remained poor for two decades. SSP sampling for bass was suspended after 1993 because catch
rates were low and bass habitat remained poor. Bass tournament results were modest over the
next decade, but average winning weights have improved since 2007 (Fig. 3).
High water in 2007 was
expected to produce a strong
year class of bass, and the
ODWC sunk about 60 cedar
trees in shallow water zones in
two “no-wake” coves in the
winter of 2008-’09, to improve
bass fishing. In 2009, high
water provided improved
sampling conditions by
flooding shoreline willows, and
an electrofishing sample was
taken for the first time in 15
years.
The abundance of largemouth bass in 2009 (45.8/ hr) exceeded the state average (40/ hour) for
the first time ever at Fort Cobb (Table 2). The catch rate of bass over 14 inches was 26.8, or 2.5
times the state average of 10 (Fig. 4). Those high catch rates now rank Fort Cobb as one of
Oklahoma’s “Quality Bass Lakes.” Shallow brush piles (cedar trees) produced an average of 1
bass per 2 trees during electrofishing, and flooded willow trees produced many spawning pairs.
Florida largemouth bass were stocked into Fort Cobb by the ODWC from 1973 to 1988, but
genetic influence could not be determined because few young bass could be collected for testing.
No bass over 10 pounds have been reported by anglers, and none have been sampled by
electrofishing. No bass over 8 pounds have been weighed-in during bass tournaments at Cobb in
the last decade. The ODWC collected two bass over 9 pounds in the 2009 survey, the largest
weighing 9.5 pounds. The lake record largemouth bass, caught in 2009, weighed 7.6 pounds.
Two-hundred smallmouth bass (average length = 10 inches) were transferred from Lake
Lawtonka to Fort Cobb in 2003. In 2009, two smallmouth bass were sampled by electrofishing
(10 inches and 14 inches long), and both were from subsequent spawning by the original stocked
fish. Anglers report occasional catches, but a fishery has not developed to date for smallmouth
bass.
0
5
10
15
20
'01 '02 '03 '04 '05 '06 '07 '08 '09
Year
Pounds
Figure 3. Bass tournament success at Fort Cobb Reservoir, 2001 - 2009
(average winning weight).
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Crappie
Crappie abundance was historically low in gill net samples at Fort Cobb, and remained below the
state average through 1999 (Table 3). The ODWC constructed and maintained several brush
piles to attract crappie, but fishing was spotty. Anglers occasionally reported good catches,
particularly in the spawning season, but the lake has not been known as a destination lake for
crappie anglers until recently.
Beginning with the 2001 sample, gill nets began to show a marked improvement in crappie
numbers. High water in 2007 was expected to produce a strong year class of crappie, and the
latest sample (2008) found the highest abundance ever for crappie at Fort Cobb.
Gillnet samples in 2001, ’03 and ’08 found
numbers of crappie over 10 inches to be 4-times
the state average. Relative weights for large
crappie were exceptional.
Trap nets set in November, 2009, captured 105
crappie for length-at-age analysis. Equal
numbers of black and white crappie were
sampled, and growth was good. At age 1.5,
crappie were about 8 inches long, at age 2.5
they averaged 10.5 inches, and at 3.5 years, they
grew to 12 inches (Table 4).
Angling for crappie at Fort Cobb appears to be
improving. High water levels will improve
spawning, and natural vegetation along with
artificial cover will help sustain that population
trend.
Figure 4. Electrofishing catch rates for largemouth bass at Fort Cobb Reservoir, 1978-2009.
State average
(Total)
11
Walleye and Saugeye
Walleye were a popular addition at Fort Cobb in the 1970s, but
their numbers were marginal in fall gillnet samples from 1978 to
1999. Walleye reproduced, but year classes were generally small
compared to other western Oklahoma lakes. Stockings of fry and
fingerlings failed to supplement spawning (Fig. 5).
Saugeye stockings began in 1998 at Fort Cobb, with sampling
catch rates and angler success rising quickly over the following
decade (Table 5). The sampling catch rate in 2006 was the
highest ever recorded in Fort Cobb for either walleye or saugeye
(Fig. 5). High water and losses through the outlet gates in 2007
probably caused the sharp decline in saugeye in the 2008 sample,
but the population should rebound with continued stockings.
Saugeye fishing was restricted by the statewide 18-inch walleye/saugeye limit until 2002, then
replaced by a 14-inch limit at Fort Cobb to prevent slow growth found at some other lakes.
Growth rates for saugeye were excellent in the ’06 sample, with stocked fish growing to an
average of 12 inches by fall, and 18 inches in 2.5 years. In the ’08 sample, saugeye grew to 11
inches their first season, and to 17 inches in just 1.5 years.
A state record saugeye of 10 pounds, 10 ounces was caught in March, 2006 by fishing guide,
Curt Wilkerson. Anglers regularly catch saugeye over 5 pounds at Fort Cobb.
Figure. 5. Historic gillnet catch rates for walleye and saugeye from sampling by the ODWC at Fort Cobb Reservoir.
12
White bass
Sand bass have been moderately abundant at Fort Cobb since standardized sampling began in
1978. The population abundance fell in 1988, and then rebounded to more than double the state
average from 1993 to 1999. Catches of sand bass over 12 inches in gill nets peaked in the ’96
and ’99 samples (Table 6).
Anglers reported a fish kill to the ODWC in April, 2001. An investigation found many dead
white bass (and no other species) in coves and arms on the lake’s east side following a strong
southwest wind. Similar kills limited to white bass were reported in lakes across the Midwest
and in Oklahoma in previous years, indicating a viral source of mortality.
White bass catches by anglers and the ODWC have been limited since 2001. Gill nets sampled
none in ‘06, and just 10 in’08. Since adults are still present to spawn, white bass are likely to
make a comeback as they did after the low point in 1988.
Hybrid Striped Bass
The first hybrid stripers were stocked in Fort Cobb in
1981, and gillnet sampling documented survival and
modest catch rates through the 1990s. Following the
white bass kill in 2001, the ODWC stocked hybrid
stripers in 8 out of 9 years to help fill the void.
The highest catch rate was then recorded in 2008, at 19
per net (Fig. 6). The sample in 2006 found the highest
catch rate for hybrids over 20 inches (2.6/net; Table 7)
With high shad abundance, hybrid growth rates and relative weights are good. Fish from the ’08
sample reached 17 inches in 2.5 years, and grew to 22 inches in 3.5 years. In 2009, the lake
record of 18.2 pounds was caught by 14-year-old Brooke King.
Figure. 6. Gillnet catch rates for white bass and hybrid stripers from sampling by the ODWC at Fort Cobb Reservoir.
13
Catfish
Fort Cobb has long been known as a catfish destination for
Oklahoma anglers. Channel catfish were average in
abundance in the first sample in 1978 and in the 1988
sample, but below the state average in the six other samples
taken before 1993 (Fig. 7). The 1988 sample was probably
exceptional due to the rare stocking of 3,400 catfish
averaging 9 inches in that year.
Prior to 1993, channel catfish were stocked frequently at 3
to 5 inches in length, with no significant improvement in
the population at Fort Cobb. After 1993, the stocking size
was raised to > 7 inches, and the channel catfish abundance
doubled in the 1994 sample. Adjustments were made to
stocking rates over the next decade, and samples since
2003 have found sustained catch rates approximately 1.5-
times the state average, due to the 7-inch stocking strategy.
Catches of channel catfish over 12 inches have been high in gill nets as well and channel catfish
over 16 inches are 3-times more common than they were prior to the stocking change in 1993
(Table 8). An experiment using baited hoop nets in 1999 captured 806 channel catfish, with a
mean length of 10.5 inches and a length range of 3 to 25 inches.7
State average
(total)
Figure. 7. Historic gillnet catch rates for channel catfish from sampling by the ODWC at Fort Cobb Reservoir.
<Before After > <7-inch stockings>
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Blue catfish were introduced to Fort Cobb in 1967, and
one fish was collected in the 1978 gillnet sample. The
population has since grown, reaching a record high in
1999 of more than 5 times the state average (Table 9).
A summer electrofishing sample was taken in 2005, and
228 blue catfish were captured in two hours of sampling
time. The largest weighed 27 pounds. Fish below 26
inches had fair body condition factors, but those over
26 inches had high relative weights (Wrs). Less than
one percent (6 of 228) of the sampled blue cats were
over 30 inches in the 2005 sample.
Anglers fish for blue cats primarily with jug lines and
surf rods at Fort Cobb with good success. Abundant
gizzard shad provide plenty of forage for blues. Blue
catfish over 10 pounds are common, and the lake record
of 52 pounds was caught in 2009.
Flathead catfish have been collected in most samples from Fort Cobb, but numbers have been
low. Jugline and trotline anglers catch large flatheads frequently, and the lake record was
established at 66 pounds in 2009.
Gizzard Shad
Sampling for gizzard shad was conducted by spring electrofishing and fall gill netting since
1978, and large shad were usually abundant at Fort Cobb. Recent sampling with small meshes in
gill nets provided more accurate data on small shad that are important for the growth of most
sport fish. Catch rates for shad under 6 inches were high from 1999 through 2008 (Table 10).
The catch rate of shad less than 6 inches did not increase significantly after the white bass kill in
2001, according to gillnet sampling. However, angler reports and first-hand observations agreed
that schools of small shad were more prolific in following summers. The increased numbers of
hybrid striped bass and saugeye should take advantage of these small shad, and eventually
reduce their numbers.
Threadfin shad are not present at Fort Cobb and are not expected to survive winter temperatures
in the relatively shallow lake. Transfers of threadfin shad at nearby lakes Lawtonka and
Thunderbird did not result in sustained populations due to winterkills.
Other Fish Species
“Rough fish” like common carp, longnose gar, river carpsucker, drum, and black bullheads are
common in Fort Cobb. A summary in the 2000 SSP report found that numbers of those species
had not changed significantly since 1978.6 Smallmouth buffalo are also present in low numbers.
Sunfish are common and provide forage for predators, and the “minnow” population includes
golden shiners, abundant inland silversides, and some robust logperch.
15
Threats to the Fishery
Poor water quality is the biggest threat to fishing in the future at Fort Cobb. Nutrients can
increase fish production, but beyond tolerable limits those nutrients can cause fish kills and
increase the chances and severity of fish disease. Agency efforts to reduce nutrient loading in
the Fort Cobb watershed should be supported. Best-use farming practices that minimize
fertilizer application and soil erosion should be encouraged in the watershed.
In the long term, siltation threatens the lifespan of Fort Cobb Reservoir and its value to anglers
and other water users. In its first 50 years, the lake has lost 10 percent of its original volume due
to siltation from unstable soils and poor conservation practices in the watershed. Shallow mud
flats in the upper one-quarter of the lake make those waters unproductive for sport fish and
anglers.
Fort Cobb Reservoir is probably not threatened by fish kills from golden algae blooms due to its
low salt content, but it is vulnerable to zebra mussels that are moving westward from
northeastern Oklahoma. Zebra mussel DNA has been detected in water samples from Fort Cobb,
but no veligers or adults have been found so far. To slow the spread of these and other aquatic
nuisance species, anglers should wash their boats and fishing equipment when moving between
lakes to fish. No lake-specific fish consumption advisories have been posted for Fort Cobb
Reservoir.
While water levels have been stable in recent years, limited alternative supplies and population
growth could increase water use in the district and beyond. Stable to higher-than-average water
levels are positive for sport fish spawning and growth. Potential for increased water use and
water level reductions should be viewed with their negative impacts to fishing considered.
Access Facilities
Boaters enjoy excellent access to Fort Cobb
Reservoir. Seven boat ramps are available, each
with a good dock adjacent to it. Four of the boat
ramps in the south half of the lake have docks that
were installed cooperatively by the State Park and
the ODWC in the 1990s. Those docks remain in
relatively good shape, and maintenance should
continue by State Park staff. Three docks and
parking lots in the north half of the lake are
maintained by the ODWC.
A full-service marina is located in the State Park, in the southeast arm. A new fishing dock is
due to be installed next to the marina in the state park soon. The park provides new restroom
facilities, RV hookups, and plenty of boat trailer parking near each of its boat ramp areas.
Access for bank anglers is available in parts of the State Park and the Wildlife Management
Area. However, access has been restricted to several key fishing points by the agencies in efforts
16
to control vandalism and crime. Older anglers or those with
restricted mobility have few choices due to vehicular access
restrictions along the lake shore.
If access to these areas was limited to users with fishing and
hunting licenses in the WMA, or other fee-based permit in the
State Park, litter and crime would likely be reduced. It might
then be possible to open up additional areas for anglers. Some
key vehicular access areas could be opened only to anglers with
disabilities.
Recommendations
Fish Habitat
 Aquatic vegetation has increased at Fort Cobb in recent years, and high water levels will
help maintain this important habitat for bass and sunfish. The Fort Cobb Master
Conservancy District should continue to encourage water conservation by users to
minimize water level reductions in the critical summer period.
 The District should also consider that additional water sales and usage may have negative
impacts on fishing and overall recreational quality Fort Cobb Reservoir.
 The ODWC should consider restricting two coves in the ODWC-managed portion to “no
wake” speed, to reduce conflict from other boaters, and to install shallow-water brush
piles to enhance bass and crappie angling.
Boating and Fishing Access
 Boat docks and ramps are generally in good shape, and maintenance should continue to
keep them safe and convenient for the public.
 A rule should be considered by the ODWC to only allow access in the Fort Cobb WMA
to licensed anglers and hunters, to reduce non-related uses, crime and trash.
 Shoreline access should be opened in key areas strictly for vehicles of physically-impaired
users.
 New boat ramp, parking and dock facilities could be built on the north side of “Marina
Cove,” to provide closer boating access for campers on that side of the cove.
17
Recommendations (cont’d)
Fishing Regulations
 The 14-inch limits on black bass and saugeye should be retained indefinitely.
Fish Stockings
 Channel catfish should be stocked with a minimum size of 7 inches at 2.5 per acre
annually (10,800).
 Saugeye should be stocked every year at 10/acre (43,000).
 Hybrid striped bass should be stocked annually at 10/acre (43,000) until white bass
numbers return to average. Thereafter, hybrids should be stocked every-other-year.
Fish Sampling
 Black bass should be sampled every 2 years (2011, 2013) by spring electrofishing to
monitor the recent improvement in habitat and any associated increase in bass abundance.
Electrofishing should be conducted only when water levels are above-normal in spring.
 Fort Cobb should be gill-netted every 3 years (2011, 2014) to assess changes in shad,
saugeye, hybrid striper, white bass and channel catfish abundance and growth rates, and
to fine-tune stocking strategies.
 Crappie should be trap-netted again in 5 years (2014) to follow trends in their abundance
and growth.
 Blue catfish should be sampled again by summer electrofishing in 5 years (2014) to
determine whether the statewide harvest restriction, enacted in 2010, was effective.
18
Citations
1. Fairchild, J., et al. 2004. An Integrated Assessment of the Trophic Status of Fort Cobb
Reservoir, Oklahoma. U.S. Geological Survey. 93p.
2. Oklahoma Water Atlas. 1999-2008. Oklahoma Water Resources Board. 31 December
2009. http://www.owrb.ok.gov/news/publications/wa/lakes/FortCobb.php
3. Ferrari, R. L. 1994. Fort Cobb Reservoir 1993 Sedimentation Survey. Bureau of
Reclamation Technical Report.
http://www.usbr.gov/pmts/sediment/projects/ReservoirSurveys/Reports/Fort%20Cobb%2
0Reservoir%201993%20Sedimentation%20Survey.pdf 41p.
4. Oklahoma’s Beneficial Use Monitoring Program-Lakes Sampling. 2006-2007 Draft
Report. Fort Cobb Reservoir.
http://www.owrb.ok.gov/quality/monitoring/bump/pdf_bump/current/lakes/fort_cobb.pdf
5. Oklahoma Conservation Commission, 2007. Fort Cobb Watershed Implementation
Project. Final Report. 42p.
6. Watkins, P. 2000. Fish Management Survey and Recommendations for Fort Cobb
Reservoir. Oklahoma Federal Aid Project F-45-D-5-001. Annual Performance Report.
23p.
7. Cunningham, K.K, and Cofer. L.M. 2000. Evaluation of the Related Catch Rates of Hoop
Nets for Sampling Channel Catfish. Proc. Annu. Conf. Southeast. Assoc. Fish and Wildl.
Agencies 54:80-87
Note- A draft of this report was sent to Fort Cobb Reservoir agency officials and then presented
to anglers at a public hearing in January, 2010. Comments from that meeting were considered in
the final plan.
19
Note of Thanks
We would like to express our gratitude for the many years of effort in sampling and managing
the fishery at Fort Cobb Reservoir by Eugene Wheeler (retired), and the late Paul Watkins, who
spent many days on the lake to improve fishing. Their work provided the foundation for this
report.
“There’s a blue cat on the bottom,
And a bullfrog on the bank.
I just pitched a pretty pebble
And watched the ripples while it sank.
The crickets in the willow
Singin’ songs they’ve always sung.
I’ve got nothin’ to do,
And I’m not leavin’ ‘til I’m done.”
Walt Wilkins
20
Date Species Number Size (in)
1959 Largemouth Bass 50,000
Channel Catfish 50,000
Crappie 15,000
Redear 15,000
1967 Blue catfish 27 2-7 lbs. each
1968 Walleye 200,000 Fry
1969 Walleye 310,000 Fry
1970 Walleye 548,004 Fry
1972 Walleye 150,000 Fry
1973 Walleye 552,977 Fry
Florida Largemouth Bass 775 Fingerling
1974 Walleye 946,727 Fry
Florida Largemouth Bass 750 Fingerling
1975 Hybrid Largemouth Bass 20,000 Fry
1976 Florida Largemouth Bass 25,000 Fingerling
1978 Channel Catfish 272,000 3.5 – 4.0
1979 Channel Catfish 41,920 3.75
1980 Florida Largemouth Bass 70,870 1.00
Hybrid Striped Bass 423,000 Fry
1981 Florida Largemouth Bass 48,240 2.00
Channel Catfish 90,000 5 -6
1982 Hybrid Striped Bass 390,536 Fry
Florida Largemouth Bass 83,000 2.50
Channel Catfish 84,000 4 -5
1983 Hybrid Striped Bass 300,000 Fry
Florida Largemouth Bass 5,060 2.00
1984 Walleye 407,000 Fry
Hybrid Striped Bass 198,000 Fry
Channel Catfish 28,115 3.00
1985 Redear 300,000 1.00
1986 Florida Largemouth Bass 41,000 2.00
Hybrid Striped Bass 43,600 1.50
Channel Catfish 82,000 3.00
1987 Largemouth Bass 41,000 1.5 -2
Hybrid Striped Bass 62,500 1.25
Channel Catfish 30,550 4.00
1988 Walleye 328,000 Fry
Hybrid Striped Bass 41,260 1.5 -2
Intergrade Florida LMB 23,550 3.00
Channel Catfish 3,400 9.00
Channel Catfish 36,250 4 - 5
1989 Walleye 41,000 1.25
Channel Catfish 20,016 5.00
Table 1. Species, number and size of fish stocked at Fort Cobb Reservoir, 1959 – 2009.
21
1990 Channel Catfish 52,650 5 -6
Walleye 212,800 1 - 1.25
1991 Hybrid Striped Bass 56,000 1.25 1.50
Channel Catfish 76,380 4 - 4.5
1992 Channel Catfish 81,000 4 - 4.5
1993 Hybrid Striped Bass 41,000 1.25
Channel Catfish 82,000 7 - 8
1994 Channel Catfish 44,000 7.00
1995 Walleye 42,600 1.50
Hybrid Striped Bass 66,300 1.25
1996 Channel Catfish 19,554 6.00
1997 Channel Catfish 4,675 9.00
1998 Saugeye 750,000 Fry
Hybrid Striped Bass 41,200 1.25
Channel Catfish 24,000 7.00
1999 Channel Catfish 20,760 7.00
Saugeye 85,000 1.25
2000 Saugeye 82,000 1.00
Hybrid Striped Bass 41,400 1.35
2001 Saugeye 45,000 1.50
Channel Catfish 20,500 4.50
2002 Saugeye 34,500 1.25
Hybrid Striped Bass 41,000 1.25
2003 Smallmouth Bass 190 5 - 12
Channel Catfish 20,500 7.00
Hybrid Striped Bass 43,000 1.25
2004 Channel Catfish 12,635 7.0 -7.6
Saugeye 40,670 1.50
Hybrid Striped Bass 41,250 1.5 -2.0
2005 Channel Catfish 10,348 7.0 – 9.0
Saugeye 43,500 1.5
Hybrid Striped Bass 41,800 1.30
2006 Channel Catfish 10,250 7.00
Saugeye 73,550 1.7 – 1.9
2007 Saugeye 81,734 1.25-1.70
Hybrid Striped Bass 41,000 7.00
Channel Catfish 12,023 7.00
2008 Channel Catfish 9,230 9.6-10.6
Hybrid Striped Bass 43,736 1.35
Saugeye 42,000 1.80
2009 Saugeye 42,390 1.80-2.00
Hybrid Striped Bass 44,604 1.40
Channel Catfish 9,642 10.9-11.00
22
Standardized Survey Data Tables
Table 2. Total number (No.), catch rates (C/f- number per hour), and relative weights (Wr) by size groups
of largemouth bass collected by spring electrofishing from Fort Cobb Reservoir. Numbers in
parentheses represent acceptable C/f values for a quality fishery. Acceptable Wr values are >90.
Total <8 inch 8-14 inch > 14inch
(>40) (15-45) (15-30) (>10)
Year No. C/f C/f Wr C/f Wr C/f Wr
1978 50 15.4
1981 262 29.9 4.9
1983 197 14.1 4.2
1988 119 18.3 3.7 92 6.8 7.8 108
1990 97 20.4 5.5 87 7.0 8.0 99
1993 69 15.3 4.0 109 7.1 4.2 105
2009 149 45.8 2.8 93 8.6 103 26.8 113
Table 3. Total number (No.), catch rates (C/f), and relative weights (Wr) by size groups of crappie
collected by fall gill netting from Fort Cobb Reservoir. Numbers in parentheses represent acceptable C/f
values for a quality fishery. Acceptable Wr values are >90.
Total <8 inch > 8 inch > 10
(>4.8) (1.2 - 7.2) (> 1.9) (>.96)
Year No. C/f C/f Wr C/f Wr C/f Wr
1978 8 1.5
1981 3 0.7
1983 8 1.4
1984 18 1.7
1987 33 3.4 2.9 92 0.5 91 trace 109
1988 43 4.4 3.7 111 0.7 103 0.4 97
1990 7 0.7 0.4 109.8 0.4 109 0.2 112
1992 49 4.8 4.4 105 0.5 91 trace 91
1993 105 3.4 2.0 99 1.4 100 0.8 102
1994 29 3.0 1.8 101 1.2 93 0.6 93
1995 57 4.2 2.7 102 1.3 91 0.6 89
1996 48 3.4 2.6 107 0.9 97 0.6 102
1999 52 5.2 1.9 92 3.3 89 1.3 95
2001 163 16.3 10.8 99 5.5 109 5.1 108
2003 59 11.8 3.6 98 8.2 103 4.1 107
2006 28 5.6 3.2 2.4 106 2.2 107
2008 217 21.7 15.1 147 6.6 101 4.3 103
23
Table 4. Mean length at age of crappie collected by fall trap netting from Fort Cobb Reservoir. Numbers
in parentheses represent values for acceptable growth rates.
Age 1 Age 2 Age 3
(> 6 in) (> 8 in) (> 9 in)
Year
2009 8 in 10.5 12
Table 5. Total number (No.), catch rates (C/f) of walleye collected by gill netting from Fort Cobb
Reservoir.
Total
Year No. C/f
1978 4 0.7
1981 13 2.6
1983 6 1.2
1984 7 0.7
1987 4 0.5
1988 6 0.7
1990 16 1.6
1992 2 0.2
1993 125 4.0
1994 20 2.0
1995 26 1.9
1996 14 0.9
1999 13 1.3
2001 2 0.2
2003 0 0.0
2006 0 0.0
2008 0 0.0
Table 6. Total number (No.), catch rates (C/f), and relative weights (Wr) by size groups of saugeye
collected by fall gill netting from Fort Cobb Reservoir. Numbers in parentheses represent acceptable C/f
values for a quality fishery. Acceptable Wr values are >90.
Total < 14 inch 14-18 inch >18 inch
Year No C/f C/f C/f C/f Wr
1999 38 3.6 3.1 0.0
2001 112 11.2 1.8 6.7 2.7
2003 50 10.0 0.2 4.0 5.8 92
2006 92 18.4 6.1 5.7 6.8 100
2008 62 6.1 3.2 2.6 0.2 95
24
Table 7. Total number (No.), catch rates (C/f), and relative weights (Wr) by size groups of white bass
collected by fall gill netting from Fort Cobb Reservoir. Numbers in parentheses represent acceptable C/f
values for a quality fishery. Acceptable Wr values are >90.
Total <8 inch 8-12 inch > 12
(>4.8) (>1.2) (1.2-7.2) (>2.4)
Year No. C/f C/f Wr C/f Wr C/f Wr
1978 54 10.9
1981 37 7.4
1983 34 6.7
1984 162 16.3
1987 14 1.5 0.5 89 0.7 78 0.2 86
1988 8 0.7 trace 97 0.4 72 0.4 87
1990 64 6.4 3.8 88 1.1 94 1.6 91
1992 26 2.5 trace 0.7 84 1.8 76
1993 337 11 6.8 85 1 83 3 90
1994 95 9.6 2.8 93 5.8 86 1.2 86
1995 174 12.3 1.9 85 9.4 82 1 78
1996 169 12.2 4.5 90 3.6 90 4.1 88
1999 99 10 3.7 91 3 91 3.3 86
2001 19 1.8 trace 102 1.6 107 trace 93
2003 25 5 1.7 97 1.9 95 1.4 100
2006 0 0 0 0 0
2008 10 1 0 0.8 0.2
25
Table 8. Total number (No.), catch rates (C/f), and relative weights (Wr) by size groups of hybrid striped
bass collected by fall gill netting from Fort Cobb Reservoir. Numbers in parentheses represent
acceptable C/f values for a quality fishery. Acceptable Wr values are >90.
Total <12 inch 12-20 inch > 20 inch
>.03 >.05 >.02
Year No. C/f C/f Wr C/f Wr C/f Wr
1981 1 0.2
1983 4 0.7
1984 2 0.2
1987 40 4.1 2.7 77 1.5 82 0.0
1988 11 1.1 trace 81 1.1 79 0.0
1990 28 2.9 0.0 1.8 90 1.1 95
1992 40 3.9 3.9 84 0.0 trace 92
1993 231 7.4 2.6 80 4.0 84 1.0 84
1994 4 0.4 0.0 0.4 82 0.0
1995 20 1.5 1.0 78 0.2 77 trace 82
1996 40 2.8 trace 85 2.4 84 0.2
1999 15 1.5 trace 75 0.9 81 0.6 85
2001 17 1.6 0.0 1.4 95 0.2 88
2003 36 7.2 0.7 88 6.5 91 0.2 90
2006 42 8.4 0.0 5.8 91 2.6 93
2008 191 19.1 12.6 88 4.7 88 1.8 87
26
Table 9. Total number (No.), catch rates (C/f), and relative weights (Wr) by size groups of channel
catfish collected by fall gill netting from Fort Cobb Reservoir. Numbers in parentheses represent
acceptable C/f values for a quality fishery. Acceptable Wr values are >90.
Total <12 inch > 12 inch > 16 inch
(>.20) (>.10) (> 1.0) (>.05)
Year No. C/f C/f Wr C/f Wr C/f Wr
1978 24 4.7
1981 14 2.9
1983 9 1.9
1984 12 1.2
1987 20 1.9 1.2 100 1.0 105 0.7 107
1988 46 4.8 3.7 97 1.1 104 0.7 107
1990 33 3.3 1.1 95 2.2 96 1.1 99
1992 19 1.8 0.5 134 1.4 83 0.9 85
1993 144 4.6 2.2 92 2.4 89 1.4 92
1994 84 8.4 5.2 83 3.2 89 2.0 91
1995 56 4.0 1.7 93 2.5 88 1.5 93
1996 46 3.4 0.4 79 3.0 80 0.9 78
1999 95 9.4 6.7 82 2.8 83 1.5 85
2001 26 2.5 0.2 98 2.3 89 1.8 91
2003 30 6.0 1.9 86 4.3 81 3.1 81
2006 26 5.2 1.6 3.6 3.4
2008 67 6.7 2.6 4.1 2.0
27
Table 10. Total number (No.), catch rates (C/f), and relative weights (Wr) by size groups of blue catfish
collected by fall gill netting from Fort Cobb Reservoir. Numbers in parentheses represent acceptable C/f
values for a quality fishery. Acceptable Wr values are >90.
Total <12 inch > 12 inch > 16 inch
(>.10) (>.05) (> .05) (>.03)
Year No. C/f C/f Wr C/f Wr C/f Wr
1978 1 0.2
1981 2 0.5
1983 0 0.0
1984 8 0.7
1987 9 0.9 0.7 93 trace 91
1988 11 1.1 0.7 93 0.4 91
1990 9 0.9 0.9 98 0.0
1992 4 0.5 0.5 116 0.0
1993 48 1.4 1.4 106 trace 99 trace 106
1994 35 3.6 2.2 93 1.4 94 0.6 103
1995 18 1.3 0.6 87 0.6 85 trace 90
1996 11 0.7 0.2 107 0.6 90 trace 90
1999 125 12.6 7.8 92 4.8 83 2.8 84
2001 19 1.8 trace 1.8 86 1.2 87
2003 6 1.2 0.2 86 1.0 89 1.0 89
2006 9 1.8 0 0.4 84 1.4 92
2008 25 2.5 2.3 92 0.2 85 0.2 85
Table 11. Total number (No.), catch rates (C/f) by size groups of gizzard shad collected by fall gill
netting from Fort Cobb Reservoir. Numbers in parentheses represent acceptable C/f values.
Total < 8 inches
(>.40) (>.20)
Year No. C/f C/f
1978 104 20.8
1981 77 15.4
1983 65 13
1984 148 14.9
1987 72 7.3 0.2
1988 154 16.2 2.6
1990 215 21.5 5.4
1992 134 13.3 2.3
1993 512 16.5 1.6
1994 203 20.4 1.2
1995 333 23.8 5.4
1996 318 22.6 0.6
1999 796 79.6 55.3
2001 413 41.4 7.8
2003 419 83.8 43
2006 495 99 81.4
2008 584 58.4 44.6
28

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FORT COBB RESERVOIR
5-YEAR FISHERIES MANAGEMENT PLAN
SOUTHWEST REGION
OKLAHOMA DEPARTMENT OF
WILDLIFE CONSERVATION
2
Prepared by:
Larry Cofer, Regional Fisheries Supervisor
Ryan Ryswyk, Fisheries Biologist
And John Perry, Fisheries Technician
DECEMBER 31, 2009
Contact Information
Address:
Southwest Fisheries Region
Oklahoma Department of
Wildlife Conservation
19333 State Highway 49
Lawton, OK 73507
Phone:
580/529-2795
Email:
swrfishodwc@mptelco.com
3
Background
Fort Cobb Reservoir, a U.S. Bureau of Reclamation
project, was impounded in 1959 for flood control,
water supply, fish and wildlife propagation and
recreation. The dam is located at river mile 7.4 on
Cobb Creek, a tributary of the Washita River, in
Caddo County, Oklahoma (Lat 35E 09' 45", Long 98E
27' 00"). Cobb Creek and two other principal
tributaries (Lake Creek and Willow Creek) drain
approximately 314 square miles into the reservoir
(Figure 1). Outflows from the reservoir include
municipal and industrial pipelines to Chickasha and
Anadarko, and an outlet for Cobb Creek.
The water in Fort Cobb Reservoir is managed by the Fort Cobb Master Conservancy District,
with offices in Anadarko, Oklahoma. Land use within the Fort Cobb watershed is primarily
agricultural, with 52% cropland and 42% range and pasture land. The remaining land surface can
be broken down into various other rural categories, with less than 0.5% considered urban.1
4
Through long-term agreement, the U.S. Bureau of Reclamation leases its lands around Fort Cobb
Reservoir to the Oklahoma Department of Tourism and Recreation (State Park -south half) and
the Oklahoma Department of Wildlife Conservation (north half; Fig. 2). Fort Cobb State Park
provides camping, swimming, boating and other recreational activities. The Oklahoma
Department of Wildlife Conservation (ODWC) provides hunting, fishing and boating facilities
and camping in the Fort Cobb Wildlife Management Area. Boating is regulated by the Lake
Patrol Division of the Oklahoma Highway Patrol.
Figure 2. Map of Fort Cobb Reservoir and lands managed by State Parks and ODWC.
Legend
-Fish Attractor
5
Habitat
At normal pool elevation (1342.0' NGVD), Fort Cobb reservoir is about 7 miles long, has a
current storage capacity of 73,800 acre-feet, a surface area of 4,300 acres (6 square miles), a
mean depth of 19 ft, a maximum depth of around 60 ft., and a shoreline length of about 45
miles.2 Fort Cobb’s Shoreline Development Index (shoreline length / surface area) is 7.0,
indicating a reservoir with a moderate number of coves, points and arms.
Outflows through the dam commonly occur in the spring rainy season, but are infrequent
afterward, and the average water exchange rate (average annual outflow / lake storage volume) is
0.6, indicating a relatively long water storage period.
The Fort Cobb MCD maintains the lake level at 1342 ft. The level is reduced by just two feet, on
average, in summers due to water use and evaporation. The lowest elevation on record is 1335
from October, 1972. Lowest elevation in the last 15 years was 3 ft. below normal pool Fort
Cobb, and the lake remained nearly full through the mini-drought of 2001 – 2006. A record high
of 1352, or 10 ft. above normal, was recorded in June, 1995. In August, 2007, Fort Cobb rose to
1350 – 8 ft. above normal- after Tropical Storm Erin dropped over 12 inches of rain in the
watershed in a 48-hour period. The lake remained in flood stage for one month after the event.
Fort Cobb has no standing timber remaining
in the basin, and many of the sandy banks
are eroded. Shoreline willows and
cottonwoods are flooded occasionally,
providing temporary shallow cover for fish.
Fort Cobb supports little aquatic vegetation
since 1982, when high water and a Eurasian
milfoil control project combined to
eliminate its extensive cattails and milfoil
beds. Recently, transplantings of native
water willow and bulrush by the ODWC
have taken root in a handful of coves in the
upper end. Extensive natural beds of sago
pondweed were noted in the shallows at Fort
Cobb in summer, 2009.
Sand and sandstone are the primary substrates in most of the lake. The dam and some shorelines
in the State Park are lined with rock rip-rap, and sandstone points and drop-offs provide some
fishing habitat. Siltation is common from erosion in the watershed, and deltas formed in upper
coves are quickly populated by willow trees.
A sedimentation study conducted at Fort Cobb in 1993 determined that siltation had resulted in a
7% loss of water volume (at elev. 1342) since construction in 1959, or an average loss rate of
165 acre-feet per year.3 Assuming that trend has been consistent, about 10% of volume has been
lost to date, due to erosion of sandy topsoil from farms in the watershed. That equates to a loss of
over 480 water surface acres for recreation.
6
Water Chemistry
Water quality in Fort Cobb Reservoir has been thoroughly studied due to impacts from farming
activity in the watershed and resulting degradation of water supply and recreational values.
From sampling in 2006, Fort Cobb’s Trophic State Index (TSI) value was 65, indicating a
hypereutrophic reservoir.1 Another study in 2000-2002 found a TSI value of 67.5 The lake
ranks as “not supporting” for potential beneficial uses of fish and wildlife propagation (due to
turbidity), or for aesthetics (due to trophic status).
Secchi disk visibilities in 2002 averaged 19.5 inches in the upper end, 35.5 inches in the lower
end, and 28 inches overall. In 2006, secchi visibility averaged 24 inches. The NTU value was 13
and the true color was 20 units. Fort Cobb’s turbidity is primarily from phytoplankton in the
lower end, dominated by blue-green algae. Turbidity in the upper end is primarily from
suspended clay stirred up by wind and wave action across shallow sediments.
Sources of nutrient loading and
erosion into Fort Cobb Reservoir have
been studied, and most are non-point
contributors from farming.5 A 319
Demonstration Project has been
implemented in the Lake Creek
watershed to educate farmers and
implement best-use practices. Results
from that 10-year program will be
available in 2010.
Specific conductance at Fort Cobb
ranged from 450 to 1100 umhos, with
an average of 572. Salinity is 0.23 to
0.58ppt. Total alkalinity ranges from
113 to 129, with a lakewide average of
118 mg/l as CaCo3. Hardness
averaged 189 mg/l.
Dissolved oxygen values range from 8.8 to 12.0, with an average of 10.3. Fort Cobb is only
occasionally stratified in summer at a depth of 30 to 42 ft near the dam. Frequent high winds
generally keep the lake mixed. Reservoir pH values ranged from 7.3 to 10.7, with an average of
8.4. Average annual water temperature is 64 degrees.
A fish kill in April, 2001 resulted in the loss of nearly all adult white bass in Fort Cobb
Reservoir. An unidentified virus was suspected as the cause since species-specific white bass
kills were reported from several other reservoirs in the Oklahoma and around the Midwest near
the same period. Poor water quality was not the suspected primary cause, but may have
contributed to the severity of the kill.
7
Habitat Implications on Fishery and Management Objectives
Excessive nutrients result in dense algal blooms at Fort Cobb Reservoir, and gizzard shad are
prolific. The loss of white bass in the fish kill of 2001 further contributes to the high number of
shad in the lake. Bank erosion and sedimentation of soils from the watershed have resulted in
reduced bank contour and increased shallow water, but aquatic vegetation has not rebounded in
this favorable environment. The lack of shallow cover is a negative for species like bass and
sunfish, and instead favors open-water species like saugeye, catfish and hybrid striped bass.
Water level fluctuations below normal pool are relatively minor at Fort Cobb. Even in the mini-drought
of 2001-2006, the water level was stable. Occasional flooding contributes to better
conditions for fish spawning and growth. High water in the summer of 2007 contributed to a
strong year-class of bass and crappie.
Primary winds and wave action in summer are from the south, and strong north winds are
common after winter cold fronts. Anglers and boaters are able to find calm waters or fish windy
points on most days at Fort Cobb. Some anglers have learned to use the wind to improve their
success by fishing along windy banks for channel catfish, hybrid stripers and saugeye. Fort
Cobb’s fertility makes fishing better-than-average, compared to other waters in western
Oklahoma, but the ODWC is concerned about the potential of further fish kills and disease due
to poor water quality.
History of Fishery
Fishing at Fort Cobb Reservoir has been managed by the ODWC’s Southwest Fisheries Region
to optimize its potential since 1959. Predictably, fishing was excellent in the first 20 years (the
“new lake effect”), but that was followed by moderation in fishing success in the last 30 years.
Notably, the loss of vegetation after 1982 resulted in reduced fishing quality for largemouth bass,
sunfish and crappie. Poor habitat for bass has also led to a proliferation of rough fish like
common carp, river carpsucker and gar.
Fish were stocked heavily from Oklahoma State Fish
Hatcheries, particularly fingerling channel catfish and Florida-strain
largemouth bass (Table 1). Standardized surveys showed
no improvement in those populations from stockings. Hybrid
striped bass fry and fingerlings showed promise after they were
first stocked in 1980. Walleye were introduced in the 1970s and
a minor fishery developed. As walleye fishing success declined,
the ODWC began stocking saugeye in 1998 and the fishing
improved significantly. 6
Inland silversides were introduced as a new forage species to many Oklahoma reservoirs,
including Fort Cobb in the 1970s, but studies later determined that native predators seldom took
advantage of the small minnows. Saugeye were stocked beginning in 1998 to take advantage of
abundant silversides and shad, and a state record saugeye (10 lbs) was caught in 2006.
8
Florida largemouth bass were stocked from 1973 to 1988, but no bass over 10 pounds were
verified from anglers or sampled by the ODWC. Bass management efforts relied on a 14-inch
length limit since the 1980s, but bass fishing did not improve and poor spawning and recruitment
were found to be the limiting factors.
In recent years, bass tournaments have reported
occasional success, and an electrofishing sample in 2009
confirmed that the bass population had rebounded from
historic lows. Reservoir- (or Tennessee-) strain
smallmouth bass were transferred from Lake Lawtonka
in 2003, and a few are still present but not adding
significantly to fishery.
Brush piles have been constructed in key fishing spots
for many years to improve fishing for crappie and bass
(Fig. 2). Crappie fishing is fair, but the average size is
exceptional compared to other Oklahoma lakes.
Blue catfish were stocked in Fort Cobb by the ODWC in 1967, and an above-average fishery
exists for jug-liners and surf-rod anglers. High shad production in most years favors blue catfish.
Flathead catfish are low in abundance at Fort Cobb, but trotline anglers occasionally catch large
flatheads. The lake record caught in 2009 weighed 66 pounds.
Anglers once counted on white bass as a fishery staple, but
sand bass have not recovered from the lake-wide kill in
April, 2001. A few sand bass were captured in the most
recent gillnet sample. A similar low period was noted in
samples from 1987 and 1988, and sand bass recovered.
Hybrid striped bass were first stocked in 1980 and Fort
Cobb is one of the best lakes in Oklahoma for hybrid
fishing. Hybrids have been stocked frequently since the
2001 white bass kill, in part to fill the void. The lake record
hybrid was established in 2009 at 18.2 pounds, and anglers
regularly catch hybrids over 10 pounds.
The primary forage fish species in Fort Cobb are gizzard
shad, sunfish, inland silversides and minnows. Shad catch
rates have been high in recent samples, presumably due to
the low number of white bass since 2001.
Fort Cobb Reservoir was 50 years old in 2009. After years of standardized sampling efforts,
habitat improvements and regulation changes by the ODWC, largemouth bass abundance has
improved and anglers currently enjoy excellent fishing for saugeye, hybrid striped bass, and
catfish, and fair fishing for crappie. Boating access facilities are also excellent at Fort Cobb.
9
Current Status of the Major Fish Species
Bass
Electrofishing catch rates for largemouth bass were chronically below the state average (< 40 per
hour) since standardized sampling began at Fort Cobb in 1978. When bass habitat was
essentially eradicated with milfoil control in 1982 and high water in 1983, bass catch rates
remained poor for two decades. SSP sampling for bass was suspended after 1993 because catch
rates were low and bass habitat remained poor. Bass tournament results were modest over the
next decade, but average winning weights have improved since 2007 (Fig. 3).
High water in 2007 was
expected to produce a strong
year class of bass, and the
ODWC sunk about 60 cedar
trees in shallow water zones in
two “no-wake” coves in the
winter of 2008-’09, to improve
bass fishing. In 2009, high
water provided improved
sampling conditions by
flooding shoreline willows, and
an electrofishing sample was
taken for the first time in 15
years.
The abundance of largemouth bass in 2009 (45.8/ hr) exceeded the state average (40/ hour) for
the first time ever at Fort Cobb (Table 2). The catch rate of bass over 14 inches was 26.8, or 2.5
times the state average of 10 (Fig. 4). Those high catch rates now rank Fort Cobb as one of
Oklahoma’s “Quality Bass Lakes.” Shallow brush piles (cedar trees) produced an average of 1
bass per 2 trees during electrofishing, and flooded willow trees produced many spawning pairs.
Florida largemouth bass were stocked into Fort Cobb by the ODWC from 1973 to 1988, but
genetic influence could not be determined because few young bass could be collected for testing.
No bass over 10 pounds have been reported by anglers, and none have been sampled by
electrofishing. No bass over 8 pounds have been weighed-in during bass tournaments at Cobb in
the last decade. The ODWC collected two bass over 9 pounds in the 2009 survey, the largest
weighing 9.5 pounds. The lake record largemouth bass, caught in 2009, weighed 7.6 pounds.
Two-hundred smallmouth bass (average length = 10 inches) were transferred from Lake
Lawtonka to Fort Cobb in 2003. In 2009, two smallmouth bass were sampled by electrofishing
(10 inches and 14 inches long), and both were from subsequent spawning by the original stocked
fish. Anglers report occasional catches, but a fishery has not developed to date for smallmouth
bass.
0
5
10
15
20
'01 '02 '03 '04 '05 '06 '07 '08 '09
Year
Pounds
Figure 3. Bass tournament success at Fort Cobb Reservoir, 2001 - 2009
(average winning weight).
10
Crappie
Crappie abundance was historically low in gill net samples at Fort Cobb, and remained below the
state average through 1999 (Table 3). The ODWC constructed and maintained several brush
piles to attract crappie, but fishing was spotty. Anglers occasionally reported good catches,
particularly in the spawning season, but the lake has not been known as a destination lake for
crappie anglers until recently.
Beginning with the 2001 sample, gill nets began to show a marked improvement in crappie
numbers. High water in 2007 was expected to produce a strong year class of crappie, and the
latest sample (2008) found the highest abundance ever for crappie at Fort Cobb.
Gillnet samples in 2001, ’03 and ’08 found
numbers of crappie over 10 inches to be 4-times
the state average. Relative weights for large
crappie were exceptional.
Trap nets set in November, 2009, captured 105
crappie for length-at-age analysis. Equal
numbers of black and white crappie were
sampled, and growth was good. At age 1.5,
crappie were about 8 inches long, at age 2.5
they averaged 10.5 inches, and at 3.5 years, they
grew to 12 inches (Table 4).
Angling for crappie at Fort Cobb appears to be
improving. High water levels will improve
spawning, and natural vegetation along with
artificial cover will help sustain that population
trend.
Figure 4. Electrofishing catch rates for largemouth bass at Fort Cobb Reservoir, 1978-2009.
State average
(Total)
11
Walleye and Saugeye
Walleye were a popular addition at Fort Cobb in the 1970s, but
their numbers were marginal in fall gillnet samples from 1978 to
1999. Walleye reproduced, but year classes were generally small
compared to other western Oklahoma lakes. Stockings of fry and
fingerlings failed to supplement spawning (Fig. 5).
Saugeye stockings began in 1998 at Fort Cobb, with sampling
catch rates and angler success rising quickly over the following
decade (Table 5). The sampling catch rate in 2006 was the
highest ever recorded in Fort Cobb for either walleye or saugeye
(Fig. 5). High water and losses through the outlet gates in 2007
probably caused the sharp decline in saugeye in the 2008 sample,
but the population should rebound with continued stockings.
Saugeye fishing was restricted by the statewide 18-inch walleye/saugeye limit until 2002, then
replaced by a 14-inch limit at Fort Cobb to prevent slow growth found at some other lakes.
Growth rates for saugeye were excellent in the ’06 sample, with stocked fish growing to an
average of 12 inches by fall, and 18 inches in 2.5 years. In the ’08 sample, saugeye grew to 11
inches their first season, and to 17 inches in just 1.5 years.
A state record saugeye of 10 pounds, 10 ounces was caught in March, 2006 by fishing guide,
Curt Wilkerson. Anglers regularly catch saugeye over 5 pounds at Fort Cobb.
Figure. 5. Historic gillnet catch rates for walleye and saugeye from sampling by the ODWC at Fort Cobb Reservoir.
12
White bass
Sand bass have been moderately abundant at Fort Cobb since standardized sampling began in
1978. The population abundance fell in 1988, and then rebounded to more than double the state
average from 1993 to 1999. Catches of sand bass over 12 inches in gill nets peaked in the ’96
and ’99 samples (Table 6).
Anglers reported a fish kill to the ODWC in April, 2001. An investigation found many dead
white bass (and no other species) in coves and arms on the lake’s east side following a strong
southwest wind. Similar kills limited to white bass were reported in lakes across the Midwest
and in Oklahoma in previous years, indicating a viral source of mortality.
White bass catches by anglers and the ODWC have been limited since 2001. Gill nets sampled
none in ‘06, and just 10 in’08. Since adults are still present to spawn, white bass are likely to
make a comeback as they did after the low point in 1988.
Hybrid Striped Bass
The first hybrid stripers were stocked in Fort Cobb in
1981, and gillnet sampling documented survival and
modest catch rates through the 1990s. Following the
white bass kill in 2001, the ODWC stocked hybrid
stripers in 8 out of 9 years to help fill the void.
The highest catch rate was then recorded in 2008, at 19
per net (Fig. 6). The sample in 2006 found the highest
catch rate for hybrids over 20 inches (2.6/net; Table 7)
With high shad abundance, hybrid growth rates and relative weights are good. Fish from the ’08
sample reached 17 inches in 2.5 years, and grew to 22 inches in 3.5 years. In 2009, the lake
record of 18.2 pounds was caught by 14-year-old Brooke King.
Figure. 6. Gillnet catch rates for white bass and hybrid stripers from sampling by the ODWC at Fort Cobb Reservoir.
13
Catfish
Fort Cobb has long been known as a catfish destination for
Oklahoma anglers. Channel catfish were average in
abundance in the first sample in 1978 and in the 1988
sample, but below the state average in the six other samples
taken before 1993 (Fig. 7). The 1988 sample was probably
exceptional due to the rare stocking of 3,400 catfish
averaging 9 inches in that year.
Prior to 1993, channel catfish were stocked frequently at 3
to 5 inches in length, with no significant improvement in
the population at Fort Cobb. After 1993, the stocking size
was raised to > 7 inches, and the channel catfish abundance
doubled in the 1994 sample. Adjustments were made to
stocking rates over the next decade, and samples since
2003 have found sustained catch rates approximately 1.5-
times the state average, due to the 7-inch stocking strategy.
Catches of channel catfish over 12 inches have been high in gill nets as well and channel catfish
over 16 inches are 3-times more common than they were prior to the stocking change in 1993
(Table 8). An experiment using baited hoop nets in 1999 captured 806 channel catfish, with a
mean length of 10.5 inches and a length range of 3 to 25 inches.7
State average
(total)
Figure. 7. Historic gillnet catch rates for channel catfish from sampling by the ODWC at Fort Cobb Reservoir.
<7-inch stockings>
14
Blue catfish were introduced to Fort Cobb in 1967, and
one fish was collected in the 1978 gillnet sample. The
population has since grown, reaching a record high in
1999 of more than 5 times the state average (Table 9).
A summer electrofishing sample was taken in 2005, and
228 blue catfish were captured in two hours of sampling
time. The largest weighed 27 pounds. Fish below 26
inches had fair body condition factors, but those over
26 inches had high relative weights (Wrs). Less than
one percent (6 of 228) of the sampled blue cats were
over 30 inches in the 2005 sample.
Anglers fish for blue cats primarily with jug lines and
surf rods at Fort Cobb with good success. Abundant
gizzard shad provide plenty of forage for blues. Blue
catfish over 10 pounds are common, and the lake record
of 52 pounds was caught in 2009.
Flathead catfish have been collected in most samples from Fort Cobb, but numbers have been
low. Jugline and trotline anglers catch large flatheads frequently, and the lake record was
established at 66 pounds in 2009.
Gizzard Shad
Sampling for gizzard shad was conducted by spring electrofishing and fall gill netting since
1978, and large shad were usually abundant at Fort Cobb. Recent sampling with small meshes in
gill nets provided more accurate data on small shad that are important for the growth of most
sport fish. Catch rates for shad under 6 inches were high from 1999 through 2008 (Table 10).
The catch rate of shad less than 6 inches did not increase significantly after the white bass kill in
2001, according to gillnet sampling. However, angler reports and first-hand observations agreed
that schools of small shad were more prolific in following summers. The increased numbers of
hybrid striped bass and saugeye should take advantage of these small shad, and eventually
reduce their numbers.
Threadfin shad are not present at Fort Cobb and are not expected to survive winter temperatures
in the relatively shallow lake. Transfers of threadfin shad at nearby lakes Lawtonka and
Thunderbird did not result in sustained populations due to winterkills.
Other Fish Species
“Rough fish” like common carp, longnose gar, river carpsucker, drum, and black bullheads are
common in Fort Cobb. A summary in the 2000 SSP report found that numbers of those species
had not changed significantly since 1978.6 Smallmouth buffalo are also present in low numbers.
Sunfish are common and provide forage for predators, and the “minnow” population includes
golden shiners, abundant inland silversides, and some robust logperch.
15
Threats to the Fishery
Poor water quality is the biggest threat to fishing in the future at Fort Cobb. Nutrients can
increase fish production, but beyond tolerable limits those nutrients can cause fish kills and
increase the chances and severity of fish disease. Agency efforts to reduce nutrient loading in
the Fort Cobb watershed should be supported. Best-use farming practices that minimize
fertilizer application and soil erosion should be encouraged in the watershed.
In the long term, siltation threatens the lifespan of Fort Cobb Reservoir and its value to anglers
and other water users. In its first 50 years, the lake has lost 10 percent of its original volume due
to siltation from unstable soils and poor conservation practices in the watershed. Shallow mud
flats in the upper one-quarter of the lake make those waters unproductive for sport fish and
anglers.
Fort Cobb Reservoir is probably not threatened by fish kills from golden algae blooms due to its
low salt content, but it is vulnerable to zebra mussels that are moving westward from
northeastern Oklahoma. Zebra mussel DNA has been detected in water samples from Fort Cobb,
but no veligers or adults have been found so far. To slow the spread of these and other aquatic
nuisance species, anglers should wash their boats and fishing equipment when moving between
lakes to fish. No lake-specific fish consumption advisories have been posted for Fort Cobb
Reservoir.
While water levels have been stable in recent years, limited alternative supplies and population
growth could increase water use in the district and beyond. Stable to higher-than-average water
levels are positive for sport fish spawning and growth. Potential for increased water use and
water level reductions should be viewed with their negative impacts to fishing considered.
Access Facilities
Boaters enjoy excellent access to Fort Cobb
Reservoir. Seven boat ramps are available, each
with a good dock adjacent to it. Four of the boat
ramps in the south half of the lake have docks that
were installed cooperatively by the State Park and
the ODWC in the 1990s. Those docks remain in
relatively good shape, and maintenance should
continue by State Park staff. Three docks and
parking lots in the north half of the lake are
maintained by the ODWC.
A full-service marina is located in the State Park, in the southeast arm. A new fishing dock is
due to be installed next to the marina in the state park soon. The park provides new restroom
facilities, RV hookups, and plenty of boat trailer parking near each of its boat ramp areas.
Access for bank anglers is available in parts of the State Park and the Wildlife Management
Area. However, access has been restricted to several key fishing points by the agencies in efforts
16
to control vandalism and crime. Older anglers or those with
restricted mobility have few choices due to vehicular access
restrictions along the lake shore.
If access to these areas was limited to users with fishing and
hunting licenses in the WMA, or other fee-based permit in the
State Park, litter and crime would likely be reduced. It might
then be possible to open up additional areas for anglers. Some
key vehicular access areas could be opened only to anglers with
disabilities.
Recommendations
Fish Habitat
 Aquatic vegetation has increased at Fort Cobb in recent years, and high water levels will
help maintain this important habitat for bass and sunfish. The Fort Cobb Master
Conservancy District should continue to encourage water conservation by users to
minimize water level reductions in the critical summer period.
 The District should also consider that additional water sales and usage may have negative
impacts on fishing and overall recreational quality Fort Cobb Reservoir.
 The ODWC should consider restricting two coves in the ODWC-managed portion to “no
wake” speed, to reduce conflict from other boaters, and to install shallow-water brush
piles to enhance bass and crappie angling.
Boating and Fishing Access
 Boat docks and ramps are generally in good shape, and maintenance should continue to
keep them safe and convenient for the public.
 A rule should be considered by the ODWC to only allow access in the Fort Cobb WMA
to licensed anglers and hunters, to reduce non-related uses, crime and trash.
 Shoreline access should be opened in key areas strictly for vehicles of physically-impaired
users.
 New boat ramp, parking and dock facilities could be built on the north side of “Marina
Cove,” to provide closer boating access for campers on that side of the cove.
17
Recommendations (cont’d)
Fishing Regulations
 The 14-inch limits on black bass and saugeye should be retained indefinitely.
Fish Stockings
 Channel catfish should be stocked with a minimum size of 7 inches at 2.5 per acre
annually (10,800).
 Saugeye should be stocked every year at 10/acre (43,000).
 Hybrid striped bass should be stocked annually at 10/acre (43,000) until white bass
numbers return to average. Thereafter, hybrids should be stocked every-other-year.
Fish Sampling
 Black bass should be sampled every 2 years (2011, 2013) by spring electrofishing to
monitor the recent improvement in habitat and any associated increase in bass abundance.
Electrofishing should be conducted only when water levels are above-normal in spring.
 Fort Cobb should be gill-netted every 3 years (2011, 2014) to assess changes in shad,
saugeye, hybrid striper, white bass and channel catfish abundance and growth rates, and
to fine-tune stocking strategies.
 Crappie should be trap-netted again in 5 years (2014) to follow trends in their abundance
and growth.
 Blue catfish should be sampled again by summer electrofishing in 5 years (2014) to
determine whether the statewide harvest restriction, enacted in 2010, was effective.
18
Citations
1. Fairchild, J., et al. 2004. An Integrated Assessment of the Trophic Status of Fort Cobb
Reservoir, Oklahoma. U.S. Geological Survey. 93p.
2. Oklahoma Water Atlas. 1999-2008. Oklahoma Water Resources Board. 31 December
2009. http://www.owrb.ok.gov/news/publications/wa/lakes/FortCobb.php
3. Ferrari, R. L. 1994. Fort Cobb Reservoir 1993 Sedimentation Survey. Bureau of
Reclamation Technical Report.
http://www.usbr.gov/pmts/sediment/projects/ReservoirSurveys/Reports/Fort%20Cobb%2
0Reservoir%201993%20Sedimentation%20Survey.pdf 41p.
4. Oklahoma’s Beneficial Use Monitoring Program-Lakes Sampling. 2006-2007 Draft
Report. Fort Cobb Reservoir.
http://www.owrb.ok.gov/quality/monitoring/bump/pdf_bump/current/lakes/fort_cobb.pdf
5. Oklahoma Conservation Commission, 2007. Fort Cobb Watershed Implementation
Project. Final Report. 42p.
6. Watkins, P. 2000. Fish Management Survey and Recommendations for Fort Cobb
Reservoir. Oklahoma Federal Aid Project F-45-D-5-001. Annual Performance Report.
23p.
7. Cunningham, K.K, and Cofer. L.M. 2000. Evaluation of the Related Catch Rates of Hoop
Nets for Sampling Channel Catfish. Proc. Annu. Conf. Southeast. Assoc. Fish and Wildl.
Agencies 54:80-87
Note- A draft of this report was sent to Fort Cobb Reservoir agency officials and then presented
to anglers at a public hearing in January, 2010. Comments from that meeting were considered in
the final plan.
19
Note of Thanks
We would like to express our gratitude for the many years of effort in sampling and managing
the fishery at Fort Cobb Reservoir by Eugene Wheeler (retired), and the late Paul Watkins, who
spent many days on the lake to improve fishing. Their work provided the foundation for this
report.
“There’s a blue cat on the bottom,
And a bullfrog on the bank.
I just pitched a pretty pebble
And watched the ripples while it sank.
The crickets in the willow
Singin’ songs they’ve always sung.
I’ve got nothin’ to do,
And I’m not leavin’ ‘til I’m done.”
Walt Wilkins
20
Date Species Number Size (in)
1959 Largemouth Bass 50,000
Channel Catfish 50,000
Crappie 15,000
Redear 15,000
1967 Blue catfish 27 2-7 lbs. each
1968 Walleye 200,000 Fry
1969 Walleye 310,000 Fry
1970 Walleye 548,004 Fry
1972 Walleye 150,000 Fry
1973 Walleye 552,977 Fry
Florida Largemouth Bass 775 Fingerling
1974 Walleye 946,727 Fry
Florida Largemouth Bass 750 Fingerling
1975 Hybrid Largemouth Bass 20,000 Fry
1976 Florida Largemouth Bass 25,000 Fingerling
1978 Channel Catfish 272,000 3.5 – 4.0
1979 Channel Catfish 41,920 3.75
1980 Florida Largemouth Bass 70,870 1.00
Hybrid Striped Bass 423,000 Fry
1981 Florida Largemouth Bass 48,240 2.00
Channel Catfish 90,000 5 -6
1982 Hybrid Striped Bass 390,536 Fry
Florida Largemouth Bass 83,000 2.50
Channel Catfish 84,000 4 -5
1983 Hybrid Striped Bass 300,000 Fry
Florida Largemouth Bass 5,060 2.00
1984 Walleye 407,000 Fry
Hybrid Striped Bass 198,000 Fry
Channel Catfish 28,115 3.00
1985 Redear 300,000 1.00
1986 Florida Largemouth Bass 41,000 2.00
Hybrid Striped Bass 43,600 1.50
Channel Catfish 82,000 3.00
1987 Largemouth Bass 41,000 1.5 -2
Hybrid Striped Bass 62,500 1.25
Channel Catfish 30,550 4.00
1988 Walleye 328,000 Fry
Hybrid Striped Bass 41,260 1.5 -2
Intergrade Florida LMB 23,550 3.00
Channel Catfish 3,400 9.00
Channel Catfish 36,250 4 - 5
1989 Walleye 41,000 1.25
Channel Catfish 20,016 5.00
Table 1. Species, number and size of fish stocked at Fort Cobb Reservoir, 1959 – 2009.
21
1990 Channel Catfish 52,650 5 -6
Walleye 212,800 1 - 1.25
1991 Hybrid Striped Bass 56,000 1.25 1.50
Channel Catfish 76,380 4 - 4.5
1992 Channel Catfish 81,000 4 - 4.5
1993 Hybrid Striped Bass 41,000 1.25
Channel Catfish 82,000 7 - 8
1994 Channel Catfish 44,000 7.00
1995 Walleye 42,600 1.50
Hybrid Striped Bass 66,300 1.25
1996 Channel Catfish 19,554 6.00
1997 Channel Catfish 4,675 9.00
1998 Saugeye 750,000 Fry
Hybrid Striped Bass 41,200 1.25
Channel Catfish 24,000 7.00
1999 Channel Catfish 20,760 7.00
Saugeye 85,000 1.25
2000 Saugeye 82,000 1.00
Hybrid Striped Bass 41,400 1.35
2001 Saugeye 45,000 1.50
Channel Catfish 20,500 4.50
2002 Saugeye 34,500 1.25
Hybrid Striped Bass 41,000 1.25
2003 Smallmouth Bass 190 5 - 12
Channel Catfish 20,500 7.00
Hybrid Striped Bass 43,000 1.25
2004 Channel Catfish 12,635 7.0 -7.6
Saugeye 40,670 1.50
Hybrid Striped Bass 41,250 1.5 -2.0
2005 Channel Catfish 10,348 7.0 – 9.0
Saugeye 43,500 1.5
Hybrid Striped Bass 41,800 1.30
2006 Channel Catfish 10,250 7.00
Saugeye 73,550 1.7 – 1.9
2007 Saugeye 81,734 1.25-1.70
Hybrid Striped Bass 41,000 7.00
Channel Catfish 12,023 7.00
2008 Channel Catfish 9,230 9.6-10.6
Hybrid Striped Bass 43,736 1.35
Saugeye 42,000 1.80
2009 Saugeye 42,390 1.80-2.00
Hybrid Striped Bass 44,604 1.40
Channel Catfish 9,642 10.9-11.00
22
Standardized Survey Data Tables
Table 2. Total number (No.), catch rates (C/f- number per hour), and relative weights (Wr) by size groups
of largemouth bass collected by spring electrofishing from Fort Cobb Reservoir. Numbers in
parentheses represent acceptable C/f values for a quality fishery. Acceptable Wr values are >90.
Total <8 inch 8-14 inch > 14inch
(>40) (15-45) (15-30) (>10)
Year No. C/f C/f Wr C/f Wr C/f Wr
1978 50 15.4
1981 262 29.9 4.9
1983 197 14.1 4.2
1988 119 18.3 3.7 92 6.8 7.8 108
1990 97 20.4 5.5 87 7.0 8.0 99
1993 69 15.3 4.0 109 7.1 4.2 105
2009 149 45.8 2.8 93 8.6 103 26.8 113
Table 3. Total number (No.), catch rates (C/f), and relative weights (Wr) by size groups of crappie
collected by fall gill netting from Fort Cobb Reservoir. Numbers in parentheses represent acceptable C/f
values for a quality fishery. Acceptable Wr values are >90.
Total <8 inch > 8 inch > 10
(>4.8) (1.2 - 7.2) (> 1.9) (>.96)
Year No. C/f C/f Wr C/f Wr C/f Wr
1978 8 1.5
1981 3 0.7
1983 8 1.4
1984 18 1.7
1987 33 3.4 2.9 92 0.5 91 trace 109
1988 43 4.4 3.7 111 0.7 103 0.4 97
1990 7 0.7 0.4 109.8 0.4 109 0.2 112
1992 49 4.8 4.4 105 0.5 91 trace 91
1993 105 3.4 2.0 99 1.4 100 0.8 102
1994 29 3.0 1.8 101 1.2 93 0.6 93
1995 57 4.2 2.7 102 1.3 91 0.6 89
1996 48 3.4 2.6 107 0.9 97 0.6 102
1999 52 5.2 1.9 92 3.3 89 1.3 95
2001 163 16.3 10.8 99 5.5 109 5.1 108
2003 59 11.8 3.6 98 8.2 103 4.1 107
2006 28 5.6 3.2 2.4 106 2.2 107
2008 217 21.7 15.1 147 6.6 101 4.3 103
23
Table 4. Mean length at age of crappie collected by fall trap netting from Fort Cobb Reservoir. Numbers
in parentheses represent values for acceptable growth rates.
Age 1 Age 2 Age 3
(> 6 in) (> 8 in) (> 9 in)
Year
2009 8 in 10.5 12
Table 5. Total number (No.), catch rates (C/f) of walleye collected by gill netting from Fort Cobb
Reservoir.
Total
Year No. C/f
1978 4 0.7
1981 13 2.6
1983 6 1.2
1984 7 0.7
1987 4 0.5
1988 6 0.7
1990 16 1.6
1992 2 0.2
1993 125 4.0
1994 20 2.0
1995 26 1.9
1996 14 0.9
1999 13 1.3
2001 2 0.2
2003 0 0.0
2006 0 0.0
2008 0 0.0
Table 6. Total number (No.), catch rates (C/f), and relative weights (Wr) by size groups of saugeye
collected by fall gill netting from Fort Cobb Reservoir. Numbers in parentheses represent acceptable C/f
values for a quality fishery. Acceptable Wr values are >90.
Total < 14 inch 14-18 inch >18 inch
Year No C/f C/f C/f C/f Wr
1999 38 3.6 3.1 0.0
2001 112 11.2 1.8 6.7 2.7
2003 50 10.0 0.2 4.0 5.8 92
2006 92 18.4 6.1 5.7 6.8 100
2008 62 6.1 3.2 2.6 0.2 95
24
Table 7. Total number (No.), catch rates (C/f), and relative weights (Wr) by size groups of white bass
collected by fall gill netting from Fort Cobb Reservoir. Numbers in parentheses represent acceptable C/f
values for a quality fishery. Acceptable Wr values are >90.
Total <8 inch 8-12 inch > 12
(>4.8) (>1.2) (1.2-7.2) (>2.4)
Year No. C/f C/f Wr C/f Wr C/f Wr
1978 54 10.9
1981 37 7.4
1983 34 6.7
1984 162 16.3
1987 14 1.5 0.5 89 0.7 78 0.2 86
1988 8 0.7 trace 97 0.4 72 0.4 87
1990 64 6.4 3.8 88 1.1 94 1.6 91
1992 26 2.5 trace 0.7 84 1.8 76
1993 337 11 6.8 85 1 83 3 90
1994 95 9.6 2.8 93 5.8 86 1.2 86
1995 174 12.3 1.9 85 9.4 82 1 78
1996 169 12.2 4.5 90 3.6 90 4.1 88
1999 99 10 3.7 91 3 91 3.3 86
2001 19 1.8 trace 102 1.6 107 trace 93
2003 25 5 1.7 97 1.9 95 1.4 100
2006 0 0 0 0 0
2008 10 1 0 0.8 0.2
25
Table 8. Total number (No.), catch rates (C/f), and relative weights (Wr) by size groups of hybrid striped
bass collected by fall gill netting from Fort Cobb Reservoir. Numbers in parentheses represent
acceptable C/f values for a quality fishery. Acceptable Wr values are >90.
Total <12 inch 12-20 inch > 20 inch
>.03 >.05 >.02
Year No. C/f C/f Wr C/f Wr C/f Wr
1981 1 0.2
1983 4 0.7
1984 2 0.2
1987 40 4.1 2.7 77 1.5 82 0.0
1988 11 1.1 trace 81 1.1 79 0.0
1990 28 2.9 0.0 1.8 90 1.1 95
1992 40 3.9 3.9 84 0.0 trace 92
1993 231 7.4 2.6 80 4.0 84 1.0 84
1994 4 0.4 0.0 0.4 82 0.0
1995 20 1.5 1.0 78 0.2 77 trace 82
1996 40 2.8 trace 85 2.4 84 0.2
1999 15 1.5 trace 75 0.9 81 0.6 85
2001 17 1.6 0.0 1.4 95 0.2 88
2003 36 7.2 0.7 88 6.5 91 0.2 90
2006 42 8.4 0.0 5.8 91 2.6 93
2008 191 19.1 12.6 88 4.7 88 1.8 87
26
Table 9. Total number (No.), catch rates (C/f), and relative weights (Wr) by size groups of channel
catfish collected by fall gill netting from Fort Cobb Reservoir. Numbers in parentheses represent
acceptable C/f values for a quality fishery. Acceptable Wr values are >90.
Total <12 inch > 12 inch > 16 inch
(>.20) (>.10) (> 1.0) (>.05)
Year No. C/f C/f Wr C/f Wr C/f Wr
1978 24 4.7
1981 14 2.9
1983 9 1.9
1984 12 1.2
1987 20 1.9 1.2 100 1.0 105 0.7 107
1988 46 4.8 3.7 97 1.1 104 0.7 107
1990 33 3.3 1.1 95 2.2 96 1.1 99
1992 19 1.8 0.5 134 1.4 83 0.9 85
1993 144 4.6 2.2 92 2.4 89 1.4 92
1994 84 8.4 5.2 83 3.2 89 2.0 91
1995 56 4.0 1.7 93 2.5 88 1.5 93
1996 46 3.4 0.4 79 3.0 80 0.9 78
1999 95 9.4 6.7 82 2.8 83 1.5 85
2001 26 2.5 0.2 98 2.3 89 1.8 91
2003 30 6.0 1.9 86 4.3 81 3.1 81
2006 26 5.2 1.6 3.6 3.4
2008 67 6.7 2.6 4.1 2.0
27
Table 10. Total number (No.), catch rates (C/f), and relative weights (Wr) by size groups of blue catfish
collected by fall gill netting from Fort Cobb Reservoir. Numbers in parentheses represent acceptable C/f
values for a quality fishery. Acceptable Wr values are >90.
Total <12 inch > 12 inch > 16 inch
(>.10) (>.05) (> .05) (>.03)
Year No. C/f C/f Wr C/f Wr C/f Wr
1978 1 0.2
1981 2 0.5
1983 0 0.0
1984 8 0.7
1987 9 0.9 0.7 93 trace 91
1988 11 1.1 0.7 93 0.4 91
1990 9 0.9 0.9 98 0.0
1992 4 0.5 0.5 116 0.0
1993 48 1.4 1.4 106 trace 99 trace 106
1994 35 3.6 2.2 93 1.4 94 0.6 103
1995 18 1.3 0.6 87 0.6 85 trace 90
1996 11 0.7 0.2 107 0.6 90 trace 90
1999 125 12.6 7.8 92 4.8 83 2.8 84
2001 19 1.8 trace 1.8 86 1.2 87
2003 6 1.2 0.2 86 1.0 89 1.0 89
2006 9 1.8 0 0.4 84 1.4 92
2008 25 2.5 2.3 92 0.2 85 0.2 85
Table 11. Total number (No.), catch rates (C/f) by size groups of gizzard shad collected by fall gill
netting from Fort Cobb Reservoir. Numbers in parentheses represent acceptable C/f values.
Total < 8 inches
(>.40) (>.20)
Year No. C/f C/f
1978 104 20.8
1981 77 15.4
1983 65 13
1984 148 14.9
1987 72 7.3 0.2
1988 154 16.2 2.6
1990 215 21.5 5.4
1992 134 13.3 2.3
1993 512 16.5 1.6
1994 203 20.4 1.2
1995 333 23.8 5.4
1996 318 22.6 0.6
1999 796 79.6 55.3
2001 413 41.4 7.8
2003 419 83.8 43
2006 495 99 81.4
2008 584 58.4 44.6
28